– It was minus-5 degrees. I was perched 15 feet high in a bur oak, cold and somewhat bored. I watched as marsh grass swayed in a gusty northwest wind, drawing arcs in the snow.

That was the final day of Minnesota’s 2004 archery deer season. The sun was perched on the western horizon, and I was chilled and impatient, hoping the last half-hour of legal shooting time would pass quickly. I had been holding out for a mature buck but, since it was the last day of season, had decided I would shoot an adult doe if I had the chance. Then, through a screen of willows and alders, I spotted a lone doe on a deer trail that passed 25 yards from my stand. This was going to work out just right; last day, last light.

Or so I thought.

As the doe stepped from cover, she snapped her head to her left and stared up, directly at me. What? There was no way she had spotted me. I hadn’t moved, plus I was directly in front of a 2-foot-wide bur oak trunk. She hadn’t scented me — deer react differently when they get a whiff of a hunter. A few seconds later, she reversed her direction and ran away, tail flying high.

“December deer are different,” I thought. “Am I missing something?”

That became my favorite saying over the years when speaking about late-season bow hunting. I’ve had a number of similar situations, where there was seemingly no way deer should have seen me, but they did. I’ve been a student of whitetails my entire life, and I know when I’ve been spotted vs. being scented, or heard.

Fast forward to this fall. Remember how cold it was in early November? I was bow hunting one evening when a spike buck stepped out about 50 yards away. The rut was on, and the little buck was full of himself. He walked over to a scrape and began to work the overhanging branch. When he had satisfied himself, he turned in my direction, and immediately spotted me. He stopped, stared up at me, and then trotted off. What? My stand was in a spruce tree, and I had ample branches behind me to break up my silhouette.

Then it hit. I was wearing my cold weather camouflage coverall, hunting gear I had worn for many years but only when it was really cold. Like in December.

I had read about how deer can possibly see into the ultraviolet (UV) range, and that some hunting clothing contained UV brighteners that might cause a hunter to glow light-blue to a deer. That did it. I had been spotted by deer too many times when I shouldn’t have been. I was going to research the subject.

I was amazed at what I discovered. First of all, using a UV light, I found that the camouflage coverall I wore for years when it was cold glowed blue when exposed to UV light. Was that the reason I was being spotted by “December deer?” And just a week earlier, by the spike buck? Because it was unseasonably cold, I had been wearing that same coverall the day the spike buck spotted me.

I purchased a spray bottle of UV killer and sprayed my entire coverall, using the UV light as I went. I watched as the blue glow disappeared.

Since that day I have not been spotted by any deer. Not once. And that includes last week when I bagged a doe (a December deer) 20 yards away.

Curious, I took the UV light to a few sporting goods stores and tested the rows of camouflage hunting clothes for UV brighteners. Roughly, 80% of the clothing showed no UV light. But some clothing did to varying degrees.

But here is a caveat. If you buy UV-free clothing, take it home and wash it in laundry detergent that contains UV brighteners, then, well, your UV-free clothing is no longer UV-free. The detergent I had been using to wash all of my laundry did contain UV brighteners, even though it does not acknowledge that on the label.

Biologists have proved deer don’t have UV filters in their eyes. Humans do. Deer don’t see as well in the red end of the spectrum as we humans do, but they see better in the blue range than humans. Several studies prove deer can see UV light, although not all researchers agree to what extent.

Here’s my take on the situation. For about $50, I bought a UV light, a bottle of UV-killer spray and a bottle of UV-free laundry detergent from a company called Atsko (www.atsko.com). I followed simple directions and now my hunting clothing is UV-free.

Best of all, now that I’ve taken the simple steps to assure my hunting clothing is UV-free, I have not been spotted by any deer, including “December deer.”